The emergency core cooling system of V-407 reactor comprises three automatically initiated subsystems: (1) hydroaccumulators with nitrogen under pressure (which are traditional ECCS accumulators used for operating WWER-1000 reactors), (2) elevated hydroaccumulators open to the containment, and (3) equipment for forced emergency depressurization of the primary circuit. All these subsystems are based on the principle of passive operation providing for long term residual heat removal in case of a loss-of-coolant accident concurrent with plant blackout (i. e. AC power supply is not required for ECCS operation). Schematic diagram of emergency core cooling system is also shown in Figure XII-3.